Tell me if this is a genius idea or stupidity

[JhnBssll]

If it's a braze on we're talking about a steel frame. It's likely to be strong enough, I'd be surprised if it isn't.

As has been mentioned numerous times now it's the heat I'd be worried about, but thinking about it you're not likely to be able to apply a great deal of force with a friction shifter so you could be ok. I think you're going to have to experiment and let us know how you get on

 

[froze]

If it's a braze on we're talking about a steel frame. It's likely to be strong enough, I'd be surprised if it isn't.

As has been mentioned numerous times now it's the heat I'd be worried about, but thinking about it you're not likely to be able to apply a great deal of force with a friction shifter so you could be ok. I think you're going to have to experiment and let us know how you get on

Let me rephrase what I said, because I think I might have come across too weird. It's not like the braze on would not be strong, but a fork and a stay that is designed at the factory to accommodate disk brakes would be the strongest. Plus adding the braze on means you would have find someone who knows how to do that sort of work and that could be difficult in today's world, you could try it yourself but if you botch it up it will look horrible and destroy the surrounding paint (which will happen anyways) as well as very possibly damaging the metal making it brittle, plus you should have a jig to hold the part against the frame so you can braze it, and do to the heat issue you should probably use silver brazing because it melts at a lower temperature. Here is a video of what you'll be looking at trying to do:

View: https://www.youtube.com/watch?v=3eSOiJWUMpQ
The attach on kind of adapters I was talking about before the braze on type came up were these:

View: https://www.youtube.com/watch?v=emW7M-ZD0Pw
Those attach on type would not be near as strong as braze on but they are far easier to install. By the time you paid for the braze on adapter, and pay someone to do the braze on, and then have the bike repainted you could have bought a frame/fork with it already done and done the strongest way!

 

[mickle]

Ok, but you would still have the same problem because it only reinforces the end portion of the dropout area and not the whole fork blade or rear stay if it's for the rear.

It's going on the back.

What's the difference between the TIG welded 4130 chromoly chainstay on my 20 old Marin Kentfield hybrid and the TIG welded 4130 chromoly chainstay on a modern disc equipped touring bike?

Do you think a rear wheel lock-up on a disc brake equipped bike puts a greater load through a chainstay than a rear wheel lock-up on - for instance - a coaster brake equipped beach cruiser (with a four inch long torque arm)?

 

[mickle]

Let me rephrase what I said, because I think I might have come across too weird. It's not like the braze on would not be strong, but a fork and a stay that is designed at the factory to accommodate disk brakes would be the strongest. Plus adding the braze on means you would have find someone who knows how to do that sort of work and that could be difficult in today's world, you could try it yourself but if you botch it up it will look horrible and destroy the surrounding paint (which will happen anyways) as well as very possibly damaging the metal making it brittle, plus you should have a jig to hold the part against the frame so you can braze it, and do to the heat issue you should probably use silver brazing because it melts at a lower temperature. Here is a video of what you'll be looking at trying to do:

View: https://www.youtube.com/watch?v=3eSOiJWUMpQ
The attach on kind of adapters I was talking about before the braze on type came up were these:

View: https://www.youtube.com/watch?v=emW7M-ZD0Pw
Those attach on type would not be near as strong as braze on but they are far easier to install. By the time you paid for the braze on adapter, and pay someone to do the braze on, and then have the bike repainted you could have bought a frame/fork with it already done and done the strongest way!

I'm doing the brazing. It's a chromoly frame which is designed to be (TIG) welded - a process which requires a great deal more heat than brazing. So I'm not worried about overheating the tubing as I *might* be if I was working on a Manganese Molybdenum alloy like 531.

I'm expecting to have to replace the paint after.

I'm a plumber by the way.

 

[mickle]

Terminology I apologise, but my points still stand, the issue with using discs for this purpose will potentially be heat & disc expansion causing the 'drag' to increase as the disc warms up.

I'm not sure how much a 1.5mm bicycle disc expands sideways between cold and hot - but I tend to get faster towards the bottom of a hill so ...

 

[JhnBssll]

I'm doing the brazing. It's a chromoly frame which is designed to be (TIG) welded - a process which requires a great deal more heat than brazing. So I'm not worried about overheating the tubing as I *might* be if I was working on a Manganese Molybdenum alloy like 531.

I'm expecting to have to replace the paint after.

I'm a plumber by the way.

A fiver says it leaks...

 

[froze]

It's going on the back.

What's the difference between the TIG welded 4130 chromoly chainstay on my 20 old Marin Kentfield hybrid and the TIG welded 4130 chromoly chainstay on a modern disc equipped touring bike?

Do you think a rear wheel lock-up on a disc brake equipped bike puts a greater load through a chainstay than a rear wheel lock-up on - for instance - a coaster brake equipped beach cruiser (with a four inch long torque arm)?

I simply do not know! All I know is that when a bike comes out of the factory intended to have disk brakes the fork and the stay are more stout than anything that a add on aftermarket can do, so is the factory making their bikes with overkill or is the aftermarket thing just fine? I don't know. I can't find any long term reports of people doing the add on thing and abusing their bikes, and by abusing I mean fast down hill stuff with a lot of braking action or fully loaded touring bikes descending mountains with a lot of heavy braking, I would assume if someone is not going to be doing any hard braking frequently then the aftermarket thing should be fine. I tend to lean towards having things being over engineered myself, for example, when I bought my Lynskey it came with a Lynskey fork and since I had no idea where that fork came from, and Lynskey wouldn't tell me, I decided to swap that fork out for an Enve fork. At the time I did that Enve had rider weight limits on their forks, and the 1.0 was rated for 230 pound rider (I can't recall the weight exactly but it's close to that), and the 2.0 was rated for a 350 pound rider (that is the exact weight limit), but I only weigh 170 to 175 after the holidays (LOL!), so the 1.0 would have been fine for me plus it was about 55 grams lighter which isn't a significant amount between the two, but I decided the 2.0 would be more stout and hold up longer so I went with that one. When I use to race I rode on 36 spoke wheels when everyone else was riding on 28 to 32 spoke wheels, but mine never collapsed while others did! I do other things like that as well, but you get where I'm coming from, I would always error on the side of caution. So that's why I'm a bit leery of the aftermarket thing vs the factory thing.

 

[froze]

I'm doing the brazing. It's a chromoly frame which is designed to be (TIG) welded - a process which requires a great deal more heat than brazing. So I'm not worried about overheating the tubing as I *might* be if I was working on a Manganese Molybdenum alloy like 531.

I'm expecting to have to replace the paint after.

I'm a plumber by the way.

Well that is cool you can do it yourself, that will for sure cut the price substantially. I wish I knew how to braze!

 

[Deleted member 26715]

I'm not sure how much a 1.5mm bicycle disc expands sideways between cold and hot - but I tend to get faster towards the bottom of a hill so ...

Neither am I, I don't have any experience with cycles, but I have with motorcycles & cars, I've had motorcycles which when the disc is cold you could push the bike, but once you start to ride it will get harder & harder to maintain speed, then when you stop it's impossible to move, due to a sticking caliper. It's going to have to be experiment, put it on, try it, see if you either overheat the disc or burn the pads, might also have to play with different types of pads. It may also be best to use cable rather than hydraulic which I think you were anyway as you could potentially boil the fluid. Just a word of warning if you decide to touch the disc to see how hot it gets be prepared to burn your skin, you can ask how I know

 

[Milkfloat]

Going back to the original question if it is genius or stupidity, you know the answer - it is stupidity, but that does not mean you should not do it.